U.S. patent number 4,130,012 [Application Number 05/854,794] was granted by the patent office on 1978-12-19 for soil moisture indicator.
This patent grant is currently assigned to Design Loft Creations, Inc.. Invention is credited to W. Scott Dimmick, Charles E. Lockerby.
United States Patent |
4,130,012 |
Lockerby , et al. |
December 19, 1978 |
Soil moisture indicator
Abstract
A soil moisture indicator including a rigid planar base member
having sufficient strength to permit its partial insertion into
soil adjacent growing plants and a water absorbent member, such as
blotter paper, secured to the base member. Overlying the water
absorbent sheet adhesively secured thereto is a transparent water
impervious layer, the layer having an increment extending beyond
the longitudinal extremities of the water absorbent sheet, the
incremental portions being adhesively secured to the base member so
that abrasive forces on the water absorbent sheet during insertion
into the soil are avoided. An improved method for manufacturing the
devices in a highly efficient and automated fashion.
Inventors: |
Lockerby; Charles E. (Foster
City, CA), Dimmick; W. Scott (Sunnyvale, CA) |
Assignee: |
Design Loft Creations, Inc.
(Foster City, CA)
|
Family
ID: |
25319531 |
Appl.
No.: |
05/854,794 |
Filed: |
November 25, 1977 |
Current U.S.
Class: |
73/73;
422/537 |
Current CPC
Class: |
G01N
31/222 (20130101); G01N 33/246 (20130101) |
Current International
Class: |
G01N
33/24 (20060101); G01N 31/22 (20060101); G01N
005/02 () |
Field of
Search: |
;73/73
;116/114AM,118A,DIG.7 ;23/253TP |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gorenstein; Charles
Attorney, Agent or Firm: Olson; Thomas H.
Claims
What is claimed is:
1. An article of manufacture for indicating the moisture content of
a plant growing medium comprising an elongate rigid base member
having sufficient strength for penetration into the surface of said
medium, an elongate water absorbent sheet having length and width
dimensions less than corresponding dimensions of said base member,
a transparent impervious layer laminated to one surface of said
sheet, said layer having a width substantially equal to that of the
sheet and a length greater than the length of the sheet so as to
form an incremental portion of at least one longitudinal end of
said sheet that extends beyond said sheet, means for adhesively
securing said sheet and said incremental portion to said base
member so that said layer overlies said sheet, and a region of said
water absorbent sheet remote from said incremental portion being
treated to produce a visual effect when said sheet is wet different
from that produced when dry.
2. An article according to claim 1 including a second incremental
portion integral with said layer and extending beyond said sheet at
the end thereof opposite from first said incremental portion and
means for adhesively securing said second incremental portion to
said base member.
3. An article according to claim 1 including a second waterproof
layer substantially congruent to first said layer and having one
surface adhesively secured to said water absorbent sheet opposite
first said layer, said second layer having an incremental portion
in registry with the incremental portion of first said layer, said
adhesively securing means including means for adhesively joining
said incremental portions and means for adhesively securing said
second layer to said base member.
4. An article according to claim 3 wherein both said waterproof
layers include incremental portions that extend beyond the opposite
end of said water absorbent sheet and means for adhesively securing
last said incremental portions to one another and to said base
member.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to soil moisture indicators and particularly
to soil moisture indicators that are completely passive and are
particularly suited for use in potted plants.
2. Description of the Prior Art
U.S. Pat. No. 3,019,638 and 3,824,844 (73/73) disclose soil
moisture monitors which in construction and operation are different
from the present invention but which are intended to achieve a
purpose generally similar to that achieved by the present
invention.
U.S. Pat. No. 3,881,873 (23/253 TP) discloses a moisture indicating
probe and a method of use which also is designed to achieve the
same purpose as the present invention but which employs completely
different principles of operation.
More than a year before the filing date hereof there has been on
sale in the United States of America a device composed of a rigid
body having sufficient strength to afford insertion thereof into
soil and a water sensitive sub-assembly adhesively secured to said
rigid member that is composed of a central layer of blotter paper
laminated on opposite surfaces with congruent transparent sheets.
The transparent sheets are glued to the blotter paper and the lower
transparent sheet is in turn glued to the rigid body. The devices
that have been on sale operate satisfactorily when new but have a
relatively short life because the blotter paper, particularly when
it is wet, tends to delaminate so that the device is subject to
delamination. Delamination is likely to occur upon insertion of the
device into the soil surface.
SUMMARY OF THE INVENTION
A moisture indicator incorporating the present invention includes a
sheet of blotter paper laminated between two layers of transparent
water impervious material. The transparent layers have a width
equal to that of the blotter layer but a length greater than that
of the blotter layer so that the active element can be secured to
the rigid base member at the ends as well as throughout the inner
surface of the lower layer to the end that the strength and
longevity of the device is increased substantially. Thus, even when
the blotter paper is weakened by being wet, it is not liable to
damage because the extending end portions of the transparent layers
retain it firmly to the rigid backing member.
Thus it is an object of the invention to provide a moisture
indicator having superior longevity to those previously available.
This object is achieved by providing relatively strong transparent
impervious layers between which the blotter sheet is laminated and
providing longitudinal extensions or increments on the water
impervious layers that extend beyond the longitudinal extremity of
the blotter sheet.
Another object is to provide a method for manufacturing indicators
embodying the invention which affords rapid and automated
production.
The foregoing, together with other objects, features and advantages
will be more apparent after referring to the following
specification and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially schematic view in perspective of apparatus
for manufacturing moisture indicators according to the invention
and depicting the method of the invention.
FIG. 2 is a longitudinal side view of the active element of the
moisture indicator embodying the invention.
FIG. 3 is a cross sectional view taken along line 3--3 of FIG.
2.
FIG. 4 is an exploded view in perspective of the parts constituting
a moisture indicating device of the invention.
FIG. 5 is a side view of a moisture indicator embodying the
invention in place in potted soil.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring more particularly to the drawings and to FIG. 5,
reference numeral 12 indicates an elongate rigid base member formed
of material having sufficient strength to permit its penetration
into plant growing media such as soil S. Base member 12 can be
formed of plastic sheet having a thickness of 0.025 inches more or
less, of wood in a form conventionally seen in nurseries for
identifying potted plants, or of another material having adequate
strength and rigidity. Base member 12 has a lower end 14 which is
tapered to facilitate insertion of the same into soil S.
Adhesively secured to one surface of base member 12 is a moisture
sensitive element identified generally at 16. Moisture sensitive
element 16 includes an upper layer 18 and a lower layer 20 which
are formed of water impervious transparent material such as 5 mil
mylar or the like. Sandwiched between the upper and lower layers is
a sheet of water absorbent material 22 which can be conventional
green blotter paper having a thickness of about 20 mils. The
surfaces of transparent layers 18 and 20 that contact water
absorbent sheet 22 are provided with suitable adhesive so that the
members are firmly laminated to one another. The outer or lower
surface of layer 20 is provided with adhesive transfer tape 23
which is a water proof product having adhesive on both surfaces,
the upper surface adhering to layer 20 and the lower surface
adhering to base member 12. A suitable adhesive transfer tape is
sold by the 3M Company under the designation 3M-467.
Because impervious layers 18 and 20 have a width equal to that of
absorbent sheet 22, the lateral edges of the water absorbent sheet
are exposed to soil S. Accordingly, when soil S is moist, absorbent
layer 22 becomes moist and such moisture is transmitted by
capillary action throughout the length of the water absorbent
layer. Sheet 22 and base member 12 are provided with aligned
transversely extending lines 24a and 24b, respectively, which lines
form an indicium 24 for indicating the depth to which the device
should be inserted into soil S in order to position a part of
moisture sensitive element 16 below the surface of the soil and a
part of the element above the surface. A region of water absorbent
layer 22 in the part of element 16 above the surface of soil S is
treated so as to produce a visual effect when wet different from
that produced when dry.
Such treated region of the water absorbent layer is identified at
26. In the form of the invention shown in the drawing the treated
area is in the form of the word "moist". The treated area is formed
by waterproofing a region of the layer 22 so that such region will
not absorb water even when the balance of water absorbent sheet 22
is wet. Because the treated region stays dry, its color remains
constant irrespective of the water content of absorbent layer 22,
whereas the balance of the water absorbent layer is relatively
light when dry and relatively dark when wet. Accordingly, when
absorbent sheet 22 is dry the treated region is invisible, and when
the absorbent sheet is wet, the treated region is visible because
of contrast between the wet and dry colors of the absorbent
layer.
The method for forming moisture sensitive element 16 is depicted
schematically in FIG. 1. A strip 22s of blotter paper or like
absorbent layer is provided, such strip having a width equivalent
to the length of water absorbent layer 22. Strip 22a of water
absorbent material is fed through a two color printer 32 which
prints in a color that contrasts with that of layer 22 a line 24a
which coincides with insertion level indicium 24. The printer also
forms treated area 26 in each of a series of recurring zones that
extend transversely of strip 22s. A pattern, e.g. the word "moist",
of the water proof region is formed by imprinting on strip 22s such
pattern with a water proof material such as a hydrophic
fluoroaliphatic resin which is diluted so as to be transparent and
invisible. One material particularly suitable for printing is a
material sold by the 3M Company under the trade designation FC-805.
Accordingly, when the strip 22s exits printer 32 it has formed
thereon in transversely extending zones a series of recurring water
proof patterns and a line 24a in contrasting color that coincides
with insertion level indicium 24 on the water sensitive element
16.
Next the strip is conveyed to a roll station formed by an upper
pressure roll 36 and a lower pressure roll 38. Fed into the roll
station from above is a sheet of transparent water impervious
material 18a. Fed into the roll station from below is a layer 20a
of the same water impervious transparent material as well as a
layer of adhesive transfer tape 23a. The surfaces of layers 18a and
20a that face absorbent strip 30 are pretreated with a thermo
setting adhesive; pressure rolls 36 and 38 are heated so that, as
the layers of material pass the roll station formed by the upper
and lower rolls, a laminated assemblage is formed, the assemblage
being shaped in a direction transverse of the path of forward
movement as seen in FIG. 2.
The widths of transparent layers 18a and 20a are equal to one
another and are greater than the width of absorbent strip 22a so
that incremental portions of the transparent layers extend beyond
the edge of the absorbent layer. Such incremental portions are
identified in FIGS. 2 and 5 at 40. Because no absorbent material is
interposed between the layers at incremental portions 40, the
layers are adhesively bonded together very firmly.
When the laminated assemblage exits the roll station formed by
rolls 36 and 38 it is conveyed through a shear 42 so that
individual moisture sensitive elements 16 are produced.
The individual moisture sensitive elements are installed on
respective base members 12 by pealing the peal off layer from the
outer surface of adhesive transfer tape 23, line 24a on the element
being aligned with line 24b on the base member and the water
proofed area 26 being positioned remote from point 14. Moisture
sensitive element 16 is pressed into adhesive contact with the base
member to achieve a permanent adhesive connection between the
element and the base member. Thus the lower surface of transparent
layer 20 including incremental portions 40 are continuously
adhesively joined to the base member. Consequently when the article
is introduced into soil S, the integrity of the device will be
maintained even though absorbent layer 22 may be weakened by
moisture or the like.
The fabrication of elements 16 will be recapitulated after which
the operation of the moisture indicator will be explained in
somewhat more detail.
In one specific device designed according to the present invention
strip 22s has a width of approximately 2 and fifteen/sixteenths
inches (about 75 mm.) and transparent layers 18a, 20a and 23a have
a width of about 3 and three/sixteenths inches (about 82 mm.).
Absorbent layer 22s is first fed through printer 32 and recurrent
water proof patterns 26 are printed thereon at intervals of
approximately one-fourth inch (about 7 mm.) in width. Line 24a is
also printed. At the roll station formed by rolls 36 and 38 layers
18a, 20a and 23a are fed in and laminated to one another and to
absorbent strip 22a, the heat present in the pressure rolls
activating the adhesive on the transparent layers. Finally, the
laminated assemblage is severed into individual moisture sensitive
elements 16 which have a cross section as shown in FIG. 3 so that
the transverse edges of absorbent layer 22 are exposed. Finally,
the moisture sensitive elements are installed onto base member 12
and the article is completed.
In use, the base member is inserted into soil S, the tapered
configuration of end 14 facilitating entry of the device into the
soil. Insertion level indicium 24 is aligned with the surface of
soil S. Because incremental extensions 40 of the moisture sensitive
element are securely adhered to the base member, the moisture
sensitive element does not separate from the base member upon such
insertion or subsequent thereto. Moisture within the soil contacts
the exposed edges of absorbent strip 22 and migrates throughout the
strip due to capillary action. When the absorbent strip becomes
moist the color thereof darkens so that the water proofed pattern
26 becomes visible because it remains dry. When the water proof
pattern is no longer visible, such indicates that absorbent layer
22 is dry which in turn indicates that soil S is dry, thereby
indicating the need to add water to the soil.
Thus it will be seen that the present invention provides a soil
moisture indicator which is sturdy, easy to use and of relatively
low cost. Moreover, the method for fabricating the moisture
responsive element 16 guarantees uniformity, low cost and
satisfactory longevity of the device. Although one embodiment of
the invention has been shown and described it will be obvious that
other adaptations and modifications can be made without departing
from the true spirit and scope of the invention.
* * * * *